In the manufacturing-industries, there is often the necessity of determining the inner condition of a porous material, particularly in sheet or web form, referring to substances which are enclosed within its interior where a simple or direct access is not possible. This applies for example to the textile industry, particularly to the finishing steps where finishing agents are applied to the textile material and are absorbed by the latter. For finishing, such as dyeing, sizing, high-grade finishing, fast finish, crease resist finish, hydrophobing, mercerizing etc., a treating liquor or a gas mixture is generally applied in excess, the excess is removed after impregnation, and the textile material is further processed, for example in a reaction step, by condensing, drying, washing, applying further finishing agents, etc.
In all cases, modern economical and ecological necessities require the application of the minimum amount of treating agents. This, in turn, requires the knowledge of the amount of free, unused substances which have remained in the textile material after the finishing and reaction steps. Only if these values are known, can the preceding treatment steps be optimized as to the amount of treating agents really required. The determination of these values should be rapid and should not destroy the material to be assayed.
In this sense, the expression "analysis" as used herein means the determination of the condition within materials as defined above but also, more generally, the determination of substances contained in or on porous materials.
It is generally well known to cut samples from porous web materials and to extract substances in excess from these samples. However, these techniques partially destroy the material and make relatively large portions thereof unusable.
As to non-destructive analysis methods, European patent application No. EP-A2-0,529,455 discloses a method and a device for the continuous measurement of the presence of ionic and nonionic substances in a running textile material web. For example, a solvent is sprayed or otherwise applied from one side onto a definite region of the running web, and the solvent or the solution draining through the textile material is collected from the other side of the web. This method and device only supplies rough values since there are no definite conditions: part of the solvent necessarily remains in the web by absorption. The solvent is applied by a moving device, and there is no certainty whether the amount of solvent used throughout the application surface is uniform or not. Generally, relatively huge amounts of extracting solvents must be used which yield only very diluted extracts. Furthermore, the method cannot be used on dry textile material.
The first and major object of the present invention is to provide an apparatus which allows the exact and rapid extraction of flat, porous materials, particularly textile materials, so that the inner condition of the materials can rapidly and exactly be determined.
Another object of the invention is to provide a method as depicted above which, during extraction of the porous material, creates certain conditions and states which are reproducibly defined and which, on the other hand, allow a complete, quantitative desorption of extractible substances from the porous substrate to be assayed.
Still another object of the present invention is to provide a method of extraction and collection of the extracted fluids by means of the apparatus according to this invention, which yields liquid samples quantitatively representing the inner condition of the substrate that can easily and rapidly be assayed by using only small volumes of extracting fluid.